1. Field of the Invention
The present invention relates to an operating head for automatic machine tools, of the kind comprising:
a fork fitted up on a support having several degrees of freedom; PA1 means for the numerical control of the rotations of the fork around its axis; PA1 a support for a chuck, being fitted up on said fork and rotatable around it under a numerical control as well, in which devices are provided for allowing the head to be reconfigurated by changing the angular position of both the fork and the support for the chuck, while keeping the tool in contact with the piece to be machined.
This allows to achieve various advantages, especially when machining the outer part of the piece in by removing material for example in making contours or the like, since it is possible to reconfigurate the head without taking off the tool from the piece, preventing the signs of restarting machining from being visible.
2. Discussion of the Background
Various kinds of machine tools are known having an operating head, on which a chuck is fitted up with a connection for the tool, and the shifts of which are numerically controlled to perform even complex machining.
In particular, machines are known comprising a support arm which is movable along a set of three Cartesian axes whereto a fork is hinged which, being numerically controlled, can rotate around the axis of the arm (axis C) and to which the support for a chuck is hinged, which, being numerically controlled as well, can in turn rotate around an axis which is orthogonal to the former (axis A).
An operating head of this kind is described, e.g., in the U.S. Pat. No. 4 904 131.
In some cases these heads are indexed, i.e. they are provided with means permitting both the fork and the support of the chuck to be locked in a discrete number of angular positions around their axes, in order to enable the head to be configured according to the shape of the piece to be machined.
For this purpose the connection between the support for the chuck and the fork or between the fork and its support takes place by means of pairs of mutually engaging racks, thus locking the various components in the desired configuration.
The present invention relates in particular, although not exclusively, to such an operating head.
In the known operating heads, in order to disengage either pair of racks and achieve a new configuration by rotating either the fork or the support of the chuck or both, we always intervene by moving the rack connected with the movable component, i.e. when adjusting the angular position of the chuck, the rack connected thereto is moved, leaving at the same time fixed the rack connected to the fork, whereas, in order to rotate the fork, the rack connected thereto is moved, leaving fixed the rack connected to the supporting arm.
Up to now this solution has been universally adopted, since the shift of the rack fitted up on the fixed portion of the head turned out to be extremely complicated.
However, this solution presents the disadvantage of the need to lift the tool from the piece in order to reconfigurate the head, with the drawback that, when the tool is lowered again to resume machining, on the piece the sign of restarting remains.